The present invention relates to a continuously or periodically operated kiln for firing ceramic workpieces.
As used herein, the term "continuously operated kilns" is understood to mean the so-called tunnel kilns. The term "periodically operated kilns" is understood to mean chamber kilns, shuttle kilns and top-hat kilns.
The present invention can be used to advantage with any of the above-mentioned kiln or furnace types. Merely for reasons of simplicity and in order to avoid repetition, the invention will be described below for the example of a tunnel kiln.
In the known tunnel kilns, the material to be fired is slowly transported through the furnace chamber, for example, by means of tunnel kiln carriages, in the direction of the longitudinal axis of the kiln. The material thus passes through a heating zone, a firing zone and finally a cooling zone. During its entire trip through the furnace, care must be taken that the material to be fired is heated as uniformly as possible in the heating zone, kept at the firing temperature in the firing zone, and cooled down again in the cooling zone. Particularly when the material enters into the heating zone, extreme care must be taken to avoid local overheating, which may occur due to the more or less point-shaped contact of the burner jets on the ceramic workpiece material. To accomplish heating of the entire material in as uniform and gentle a manner as possible, it was necessary in the prior art to arrange the material at a certain distance from the surface of the transporting carriage. This was done by arranging a setting plate on the transporting carriage in a spaced relationship thereto and then stacking the material to be fired on this setting plate. However, this arrangement prevented full utilization of the available kiln volume.